mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 186

• Manufacturer Part Number: mc68hc916y3
• Description: Mc68hc16y3 16 Bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

6.3 SRAM Array Address Space Type
6.4 Normal Access
6.5 Standby and Low-Power Stop Operation
6.6 Reset
6-2
MOTOROLA
The RASP[1:0] in RAMMCR determine the SRAM array address space type. The
SRAM module can respond to both program and data space accesses or to program
space accesses only. Because the CPU16 operates in supervisor mode only, RASP1
has no effect. Table 6-1 shows RASP[1:0] encodings.
Refer to 5.5.1.7 Function Codes for more information concerning address space types
and program/data space access. Refer to 4.6 Addressing Modes for more information
on addressing modes.
The array can be accessed by byte, word, or long word. A byte or aligned word access
takes one bus cycle or two system clocks. A long word or misaligned word access re-
quires two bus cycles. Refer to 5.6 Bus Operation for more information concerning ac-
cess times.
Standby and low-power modes should not be confused. Standby mode maintains the
RAM array when the main MCU power supply is turned off. Low-power stop mode al-
lows the CPU16 to control MCU power consumption by disabling unused modules.
Relative voltage levels of the MCU V
is in standby mode. SRAM circuitry switches to the standby power source when V
drops below specified limits. If specified standby supply voltage levels are maintained
during the transition, there is no loss of memory when switching occurs. The RAM ar-
ray cannot be accessed while the SRAM module is powered from V
operation is not desired, connect the V
I
PENDIX A ELECTRICAL CHARACTERISTICS for standby switching and power con-
sumption specifications.
Reset places the SRAM in low-power stop mode, enables program space access, and
clears the base address registers and the register lock bit. These actions make it pos-
sible to write a new base address into the ROMBAH and ROMBAL registers.
SB
(SRAM standby current) values may vary while V
Table 6-1 SRAM Array Address Space Type
Freescale Semiconductor, Inc.
RASP[1:0]
For More Information On This Product,
X0
X1
STANDBY RAM MODULE
Go to: www.freescale.com
DD
Program and data accesses
STBY
and V
Program access only
pin to V
STBY
Space
pins determine whether the SRAM
SS
DD
.
transitions occur. Refer to AP-
MC68HC16Y3/916Y3
STBY
USER’S MANUAL
. If standby
DD